Lago Viedma is a large periglacial lake in Santa Cruz Province, southern Argentina, located within the UNESCO World Heritage-listed Los Glaciares National Park near the border with Chile. It measures approximately 80 kilometers in length and 15 kilometers in average width, covering roughly 1,220 square kilometers, making it the second largest perennial lake located entirely within Argentina. The lake sits at coordinates 49°35′S 72°30′W and is fed by meltwater from the Southern Patagonian Ice Field, including Glaciar Viedma — the largest glacier in Argentina — which calves icebergs directly into the western end of the lake.

The primary access point for paddlers and boat tours is Bahía Túnel (Tunnel Bay Port), located approximately 18 kilometers from El Chaltén. El Chaltén itself is reached via Provincial Route 41 from El Calafate, a drive of roughly three hours. The town of El Chaltén serves as the main base for visiting the lake, with tour operators offering catamaran and conventional vessel excursions that navigate among icebergs toward the glacier face. Kayaking on calmer sections of the lake is an option for exploring the shoreline, with views of the Fitz Roy massif to the north.

Paddlers should be aware that the lake's western shore near Glaciar Viedma is a restricted zone under regulations enforced by the Administración de Parques Nacionales (APN). Mandatory waste removal applies to all visitors, and activities that could introduce invasive species are prohibited. The presence of calving icebergs near the glacier front represents a significant hazard for independent paddlers venturing into that area.

The lake's aesthetic character is defined by its glacial origins: the water takes on distinctive tones from glacial sediment, icebergs drift across the surface, and the surrounding landscape includes the Huemul Massif to the south and the Fitz Roy and Cerro Torre peaks to the north. A short, low-difficulty trek from Cape Horn Bay to a viewpoint overlooking Iceberg Bay is accessible during organized boat excursions. Ice treks on Glaciar Viedma, previously available as guided options, are currently suspended due to ongoing glacier retreat.